High-pressure phase equilibrium of the binary systems CO₂ + 355-TMHA and CO₂ + 335-TMCHMA

The thermodynamic behaviors of the two-phase systems of 3,5,5-trimethylhexyl acrylate (355-TMHA) and 3,3,5-trimethylcyclohexyl methacrylate (335-TMCHMA) in high-pressure CO₂ are reported. The thermodynamic data were determined with the aid of a synthetic approach at temperature (T) = (313.2-393.2 K) and pressure (p) = (3.84-20.80 MPa). The acquired findings revealed that the miscibility of CO₂ was observed to raise monotonically and the augmented of model T_s and mole fraction of (355-TMHA and 335-TMCHMA) in two-component (solvent + solute) mixtures. The miscibility curves of 355-TMHA and 335-TMCHMA in the 355-TMHA + Sc-CO₂ and 335-TMCHMA + Sc-CO₂ systems increased with the temperature at a fixed pressure. The 355-TMHA + Sc-CO₂ and 335-TMCHMA + Sc-CO₂ systems exhibited type-I phase behavior. Besides, the lab-based investigational solubility was adequately compared with the value obtained using the Peng-Robinson equation of state (P-R E-S). Both the model mixtures (355-TMHA + Sc-CO₂ and 335-TMCHMA + Sc-CO₂) did not reveal 3 phases (liquid + vapor + liquid) at any of the five analyzed temperatures. The P-R E-S comparatively provided the phase behavior (PB) of the (355-TMHA + Sc-CO₂ and 335-TMCHMA + Sc-CO₂) models utilizing two T-independent mixture interaction factors. The mixture critical curves (MCC) obtained using the computational data and lab-based results had a relatively good match when the two adjustable factors of the P-R E-S were applied. The root means square deviation (RMSD) percentage (%) for the 355-TMHA + Sc-CO₂ [κ_ij = 0.040, η_ij = −0.040] and 335-TMCHMA + Sc-CO₂ [κ_ij = 0.035, η_ij = −0.040] systems ascertained at 353.2 K utilizing the two factors were 6.67% and 7.57%, correspondingly. Then, the RMSD (%) of the 335-TMCHMA + Sc-CO₂ system predicted using the adjusted values at every temperature was noted as 4.56%.